diff --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
index 88755297c8e79..b2c50f563696f 100644
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -57,6 +57,14 @@ def __init__(self, command, message):
 kPdbgRegex = "%dbg\\(([^)'\"]*)\\)(.*)"
 
 
+def buildPdbgCommand(msg, cmd):
+    res = f"%dbg({msg}) {cmd}"
+    assert re.fullmatch(
+        kPdbgRegex, res
+    ), f"kPdbgRegex expected to match actual %dbg usage: {res}"
+    return res
+
+
 class ShellEnvironment(object):
 
     """Mutable shell environment containing things like CWD and env vars.
@@ -985,7 +993,7 @@ def _executeShCmd(cmd, shenv, results, timeoutHelper):
 def executeScriptInternal(test, litConfig, tmpBase, commands, cwd):
     cmds = []
     for i, ln in enumerate(commands):
-        match = re.match(kPdbgRegex, ln)
+        match = re.fullmatch(kPdbgRegex, ln)
         if match:
             command = match.group(2)
             ln = commands[i] = match.expand(": '\\1'; \\2" if command else ": '\\1'")
@@ -1067,25 +1075,10 @@ def executeScriptInternal(test, litConfig, tmpBase, commands, cwd):
 def executeScript(test, litConfig, tmpBase, commands, cwd):
     bashPath = litConfig.getBashPath()
     isWin32CMDEXE = litConfig.isWindows and not bashPath
-    coverage_index = 0  # Counter for coverage file index
     script = tmpBase + ".script"
     if isWin32CMDEXE:
         script += ".bat"
 
-    # Set unique LLVM_PROFILE_FILE for each run command
-    for j, ln in enumerate(commands):
-        match = re.match(kPdbgRegex, ln)
-        if match:
-            command = match.group(2)
-            commands[j] = match.expand(": '\\1'; \\2" if command else ": '\\1'")
-            if litConfig.per_test_coverage:
-                # Extract the test case name from the test object
-                test_case_name = test.path_in_suite[-1]
-                test_case_name = test_case_name.rsplit(".", 1)[0]  # Remove the file extension
-                llvm_profile_file = f"{test_case_name}{coverage_index}.profraw"
-                commands[j] = f"export LLVM_PROFILE_FILE={llvm_profile_file} && {commands[j]}"
-                coverage_index += 1
-
     # Write script file
     mode = "w"
     open_kwargs = {}
@@ -1096,7 +1089,7 @@ def executeScript(test, litConfig, tmpBase, commands, cwd):
     f = open(script, mode, **open_kwargs)
     if isWin32CMDEXE:
         for i, ln in enumerate(commands):
-            match = re.match(kPdbgRegex, ln)
+            match = re.fullmatch(kPdbgRegex, ln)
             if match:
                 command = match.group(2)
                 commands[i] = match.expand(
@@ -1109,7 +1102,7 @@ def executeScript(test, litConfig, tmpBase, commands, cwd):
         f.write("\n@if %ERRORLEVEL% NEQ 0 EXIT\n".join(commands))
     else:
         for i, ln in enumerate(commands):
-            match = re.match(kPdbgRegex, ln)
+            match = re.fullmatch(kPdbgRegex, ln)
             if match:
                 command = match.group(2)
                 commands[i] = match.expand(": '\\1'; \\2" if command else ": '\\1'")
@@ -1837,13 +1830,7 @@ def _handleCommand(cls, line_number, line, output, keyword):
         if not output or not output[-1].add_continuation(line_number, keyword, line):
             if output is None:
                 output = []
-            pdbg = "%dbg({keyword} at line {line_number})".format(
-                keyword=keyword, line_number=line_number
-            )
-            assert re.match(
-                kPdbgRegex + "$", pdbg
-            ), "kPdbgRegex expected to match actual %dbg usage"
-            line = "{pdbg} {real_command}".format(pdbg=pdbg, real_command=line)
+            line = buildPdbgCommand(f"{keyword} at line {line_number}", line)
             output.append(CommandDirective(line_number, line_number, keyword, line))
         return output
 
@@ -2048,6 +2035,27 @@ def parseIntegratedTestScript(test, additional_parsers=[], require_script=True):
 
 def _runShTest(test, litConfig, useExternalSh, script, tmpBase):
     def runOnce(execdir):
+        # Set unique LLVM_PROFILE_FILE for each run command
+        if litConfig.per_test_coverage:
+            # Extract the test case name from the test object, and remove the
+            # file extension.
+            test_case_name = test.path_in_suite[-1]
+            test_case_name = test_case_name.rsplit(".", 1)[0]
+            coverage_index = 0  # Counter for coverage file index
+            for i, ln in enumerate(script):
+                match = re.fullmatch(kPdbgRegex, ln)
+                if match:
+                    dbg = match.group(1)
+                    command = match.group(2)
+                else:
+                    command = ln
+                profile = f"{test_case_name}{coverage_index}.profraw"
+                coverage_index += 1
+                command = f"export LLVM_PROFILE_FILE={profile}; {command}"
+                if match:
+                    command = buildPdbgCommand(dbg, command)
+                script[i] = command
+
         if useExternalSh:
             res = executeScript(test, litConfig, tmpBase, script, execdir)
         else:
@@ -2071,7 +2079,14 @@ def runOnce(execdir):
     # Re-run failed tests up to test.allowed_retries times.
     execdir = os.path.dirname(test.getExecPath())
     attempts = test.allowed_retries + 1
+    scriptInit = script
     for i in range(attempts):
+        # runOnce modifies script, but applying the modifications again to the
+        # result can corrupt script, so we restore the original upon a retry.
+        # A cleaner solution would be for runOnce to encapsulate operating on a
+        # copy of script, but we actually want it to modify the original script
+        # so we can print the modified version under "Script:" below.
+        script = scriptInit[:]
         res = runOnce(execdir)
         if isinstance(res, lit.Test.Result):
             return res
diff --git a/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/lit.cfg b/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/lit.cfg
index 186c81ebd1728..b83d61eec595b 100644
--- a/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/lit.cfg
+++ b/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/lit.cfg
@@ -3,6 +3,9 @@ import os
 
 config.name = "per-test-coverage-by-lit-cfg"
 config.suffixes = [".py"]
-config.test_format = lit.formats.ShTest(execute_external=True)
+config.test_format = lit.formats.ShTest(
+    execute_external=eval(lit_config.params.get("execute_external")),
+    preamble_commands=["%{python} %s | FileCheck -DINDEX=0 %s"]
+)
 lit_config.per_test_coverage = True
 config.substitutions.append(("%{python}", '"%s"' % (sys.executable)))
diff --git a/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/per-test-coverage-by-lit-cfg.py b/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/per-test-coverage-by-lit-cfg.py
index 0abe00bdedb1f..a8790f74f178c 100644
--- a/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/per-test-coverage-by-lit-cfg.py
+++ b/llvm/utils/lit/tests/Inputs/per-test-coverage-by-lit-cfg/per-test-coverage-by-lit-cfg.py
@@ -1,5 +1,6 @@
 # Check that the environment variable is set correctly
-# RUN: %{python} %s | FileCheck %s
+# RUN: %{python} %s | FileCheck -DINDEX=1 %s
+# RUN: %{python} %s | FileCheck -DINDEX=2 %s
 
 # Python script to read the environment variable
 # and print its value
@@ -8,4 +9,4 @@
 llvm_profile_file = os.environ.get('LLVM_PROFILE_FILE')
 print(llvm_profile_file)
 
-# CHECK: per-test-coverage-by-lit-cfg0.profraw
+# CHECK: per-test-coverage-by-lit-cfg[[INDEX]].profraw
diff --git a/llvm/utils/lit/tests/Inputs/per-test-coverage/lit.cfg b/llvm/utils/lit/tests/Inputs/per-test-coverage/lit.cfg
index 6e7f4c0e3bc97..9ffca93def73f 100644
--- a/llvm/utils/lit/tests/Inputs/per-test-coverage/lit.cfg
+++ b/llvm/utils/lit/tests/Inputs/per-test-coverage/lit.cfg
@@ -3,6 +3,8 @@ import os
 
 config.name = "per-test-coverage"
 config.suffixes = [".py"]
-config.test_format = lit.formats.ShTest(execute_external=True)
+config.test_format = lit.formats.ShTest(
+    execute_external=eval(lit_config.params.get("execute_external")),
+    preamble_commands=["%{python} %s | FileCheck -DINDEX=0 %s"]
+)
 config.substitutions.append(("%{python}", '"%s"' % (sys.executable)))
-
diff --git a/llvm/utils/lit/tests/Inputs/per-test-coverage/per-test-coverage.py b/llvm/utils/lit/tests/Inputs/per-test-coverage/per-test-coverage.py
index 65e4aa69bff07..59e806939a23a 100644
--- a/llvm/utils/lit/tests/Inputs/per-test-coverage/per-test-coverage.py
+++ b/llvm/utils/lit/tests/Inputs/per-test-coverage/per-test-coverage.py
@@ -1,5 +1,6 @@
 # Check that the environment variable is set correctly
-# RUN: %{python} %s | FileCheck %s
+# RUN: %{python} %s | FileCheck -DINDEX=1 %s
+# RUN: %{python} %s | FileCheck -DINDEX=2 %s
 
 # Python script to read the environment variable
 # and print its value
@@ -8,4 +9,4 @@
 llvm_profile_file = os.environ.get('LLVM_PROFILE_FILE')
 print(llvm_profile_file)
 
-# CHECK: per-test-coverage0.profraw
+# CHECK: per-test-coverage[[INDEX]].profraw
diff --git a/llvm/utils/lit/tests/allow-retries.py b/llvm/utils/lit/tests/allow-retries.py
index b8abe0ba4fee1..bf6c041933887 100644
--- a/llvm/utils/lit/tests/allow-retries.py
+++ b/llvm/utils/lit/tests/allow-retries.py
@@ -39,3 +39,15 @@
 # RUN: rm -f %t.counter
 # RUN: %{lit} %{inputs}/test_retry_attempts/test.py -Dcounter=%t.counter -Dpython=%{python} | FileCheck --check-prefix=CHECK-TEST6 %s
 # CHECK-TEST6: Passed With Retry: 1
+
+# This test checks that --per-test-coverage doesn't accumulate inserted
+# LLVM_PROFILE_FILE= commands across retries.
+#
+# RUN: rm -f %t.counter
+# RUN: %{lit} -a %{inputs}/test_retry_attempts/test.py --per-test-coverage\
+# RUN:     -Dcounter=%t.counter -Dpython=%{python} | \
+# RUN:   FileCheck --check-prefix=CHECK-TEST7 %s
+#     CHECK-TEST7: Command Output (stdout):
+#     CHECK-TEST7: LLVM_PROFILE_FILE=
+# CHECK-TEST7-NOT: LLVM_PROFILE_FILE=
+#     CHECK-TEST7: Passed With Retry: 1
diff --git a/llvm/utils/lit/tests/per-test-coverage-by-lit-cfg.py b/llvm/utils/lit/tests/per-test-coverage-by-lit-cfg.py
index 1cc3927dc8904..189c1cebd623b 100644
--- a/llvm/utils/lit/tests/per-test-coverage-by-lit-cfg.py
+++ b/llvm/utils/lit/tests/per-test-coverage-by-lit-cfg.py
@@ -1,6 +1,24 @@
 # Test if lit_config.per_test_coverage in lit.cfg sets individual test case coverage.
 
-# RUN: %{lit} -a -v %{inputs}/per-test-coverage-by-lit-cfg/per-test-coverage-by-lit-cfg.py \
-# RUN: | FileCheck -match-full-lines %s
-#
-# CHECK: PASS: per-test-coverage-by-lit-cfg :: per-test-coverage-by-lit-cfg.py ({{[^)]*}})
+# RUN: %{lit} -a -vv -Dexecute_external=False \
+# RUN:     %{inputs}/per-test-coverage-by-lit-cfg/per-test-coverage-by-lit-cfg.py | \
+# RUN:   FileCheck -DOUT=stdout %s
+
+# RUN: %{lit} -a -vv -Dexecute_external=True \
+# RUN:     %{inputs}/per-test-coverage-by-lit-cfg/per-test-coverage-by-lit-cfg.py | \
+# RUN:   FileCheck -DOUT=stderr %s
+
+#      CHECK: {{^}}PASS: per-test-coverage-by-lit-cfg :: per-test-coverage-by-lit-cfg.py ({{[^)]*}})
+#      CHECK: Command Output ([[OUT]]):
+# CHECK-NEXT: --
+#      CHECK: export
+#      CHECK: LLVM_PROFILE_FILE=per-test-coverage-by-lit-cfg0.profraw
+#      CHECK: per-test-coverage-by-lit-cfg.py
+#      CHECK: {{RUN}}: at line 2
+#      CHECK: export
+#      CHECK: LLVM_PROFILE_FILE=per-test-coverage-by-lit-cfg1.profraw
+#      CHECK: per-test-coverage-by-lit-cfg.py
+#      CHECK: {{RUN}}: at line 3
+#      CHECK: export
+#      CHECK: LLVM_PROFILE_FILE=per-test-coverage-by-lit-cfg2.profraw
+#      CHECK: per-test-coverage-by-lit-cfg.py
diff --git a/llvm/utils/lit/tests/per-test-coverage.py b/llvm/utils/lit/tests/per-test-coverage.py
index 428712e479257..cf5e82c44dc51 100644
--- a/llvm/utils/lit/tests/per-test-coverage.py
+++ b/llvm/utils/lit/tests/per-test-coverage.py
@@ -1,6 +1,24 @@
 # Test LLVM_PROFILE_FILE is set when --per-test-coverage is passed to command line.
 
-# RUN: %{lit} -a -v --per-test-coverage %{inputs}/per-test-coverage/per-test-coverage.py \
-# RUN: | FileCheck -match-full-lines %s
-#
-# CHECK: PASS: per-test-coverage :: per-test-coverage.py ({{[^)]*}})
+# RUN: %{lit} -a -vv --per-test-coverage -Dexecute_external=False \
+# RUN:     %{inputs}/per-test-coverage/per-test-coverage.py | \
+# RUN:   FileCheck -DOUT=stdout %s
+
+# RUN: %{lit} -a -vv --per-test-coverage -Dexecute_external=True \
+# RUN:        %{inputs}/per-test-coverage/per-test-coverage.py | \
+# RUN:   FileCheck -DOUT=stderr %s
+
+#      CHECK: {{^}}PASS: per-test-coverage :: per-test-coverage.py ({{[^)]*}})
+#      CHECK: Command Output ([[OUT]]):
+# CHECK-NEXT: --
+#      CHECK: export
+#      CHECK: LLVM_PROFILE_FILE=per-test-coverage0.profraw
+#      CHECK: per-test-coverage.py
+#      CHECK: {{RUN}}: at line 2
+#      CHECK: export
+#      CHECK: LLVM_PROFILE_FILE=per-test-coverage1.profraw
+#      CHECK: per-test-coverage.py
+#      CHECK: {{RUN}}: at line 3
+#      CHECK: export
+#      CHECK: LLVM_PROFILE_FILE=per-test-coverage2.profraw
+#      CHECK: per-test-coverage.py